Seasonal variation influences the semen characteristics and freezability in Xinong Saanen goat
The aim of this study was to evaluate how season of ejaculate collection influences seminal quality parameters before and after freeze–thawing of Xinong Saanen buck semen. Ejaculates were collected from eight bucks and throughout the four seasons of 1 year identified in the northern hemisphere (spring, summer, autumn and winter). During the study period, semen was collected at 10-day intervals during each season with an artificial vagina. Semen samples were evaluated by the combination of traditional and Computer-Assisted Sperm Analysis (CASA) semen assessment methods and sperm quality parameters (motility and morphology) were compared at fresh and after freeze–thawing respectively. The results demonstrated that season of ejaculate collection influenced (P< 0.05) semen quality of Xinong Saanen bucks before freezing. During spring, summer and autumn, the ejaculate subjectively motility; volume; sperm concentration; sperm output and membrane integrity were higher (P< 0.05) than in the winter. The CASA also illustrated seasonal variation greatly affected semen motility kinetic parameters. An increase in the curvilinear velocity (CLV); straight line velocity (SLV); beat cross frequency (BCF) and amplitude of lateral head displacement (LHD) was observed during spring, summer and autumn, followed by a significant (P< 0.05) decrease during the winter. Furthermore, season of ejaculate collection influenced sperm freezability. Semen characters after freeze–thawing followed a phenomenon similar to that of the fresh ejaculate except in spring. In details, sperm quality was higher (P< 0.01) in summer and autumn than in spring and winter, in terms of total motile sperm (MS); rapidly progressive motile sperm (RPMS); CLV; SLV; average path velocity (APV); BCF and LHD base on the CASA. The membrane integrity and acrosome integrity were obtained from summer to autumn were higher (P< 0.01) than in spring and winter. Consequently, it can be said that Xinong Saanen bucks have distinct seasonal spermatogenic activity, with better semen quality characteristics being recorded during spring, summer and winter before freezing. Sperm from ejaculates collected during summer and autumn are more suitable for cryopreservation. Thus, it is possible to implement intensive goat breeding strategy with two kidding seasons in one year in order to produce adequate quantities of goat milk and equalize the need for milk throughout the year, and moreover, the poor semen characteristics emphasize the need in avoiding making use of semen collection for cryopreservation purposes during spring and winter seasons of the year.
Xinong Saanen goat; Sensonality; Semen characteristics; Freezability; CASA